1. Field of this Invention
This invention relates to a process for recovering copper and noble metals from organic precipitates, residues and polymerizates.
2. Description of the Prior Art
Processes from which the above-type or residues result, are often very important in industry. For example, the oxidation of ethylene in the homogeneous phase in a solution containing hydrochloric acid, copper and palladium chloride, represents the most important process for producing acetaldehyde. It is characterized by a high level of economy and technical efficiency but a solid precipitate which forms in the contract solution during catalysis constitutes a serious disadvantage. This leads to deactivation of the content fluid so that the contact fluid cannot be used for the desired length of time but has to be periodically clarified by filtration or decanted from the precipitated metal containing substances. Also it must be enriched with new metal salts to prevent any blockages in the supply lines, in addition, to the output drop of the reactor. A particular disadvantage is the wastage or lose of costly noble metal which occurs.
Attempts were made to extract the metals from the abovementioned precipitates with acids, for example, hydrochloric acid, but these efforts were not particularly satisfactory -- polymerizates which are produced as a precipitate and which firmly encase the metals are most likely formed in the course of the catalysis.
It was also attempted to burn the slurry. However, difficulties are involved in feeding the slurry to the burner as it must either be dried sufficiently until it is solid and thus capable of being added in measured quantities or it must be mixed in water or fuel to form a paste. An extremely awkward step involved in this process is the quantitative collection of the light ash which precipitates from the combustion gases and at best a wet ash is obtained which presents new problems during subsequent processing as it may be contaminated with fuel impurities.
Proposals for distilling these residues and burning them out not only necessitate considerable expenditure on apparatus and the use of combustible material, but also involve problems with exhaust gas. For this reason, such processes have never been commercially employed.